If you can afford one of these from Hotech, you will be very happy:-
http://www.hotechusa.com/SCA%20T-Adapter.html
From Bintel, I think this is the one you need. Search "Bintel Camera Adapter 2" " on their site - $39.
"This adapter slips straight into 2" focusers providing a t-thread for attaching photographic or imaging equipment.
Minimises vignetting by providing the widest clear aperture possible using t-thread connectors.
Safety cut away on barrel to prevent equipment slipping out.
Threaded to accept 2" filters like IR-UV blocking or Deep Sky filters.
Also adds minimum back focus requiring only 6mm! "